I will continue to study glutamate activated single channel conductances in cultured hippocampal neurons using patch clamp recording techniques. Several specific experiments are planned. Establishment of a dose response relationship for the various angonists is particularly important. This information will allow us to determine the Kd's for activation of the various conductances. Permeability experiments will also be performed using symmetrical and non-symmetrical solutions of cesium, sodium and lithium salts with and without calcium. The Kd of block of the large conductance by magnesium will be determined by measuring closed times at several different voltages and different concentrations of magnesium. The effects of glutamate antagonists on the ability of the different agonists to open the various conductances will be determined. Finally, I will determine whether the different conductances are correlated in time. All of these experiments will define important biophysical parameters of glutamate-activated single channel conductances. In addition, the data obtained from all of the experiments will provide a basis from which it may be possible to determine whether glutamate activates a single channel with at least two receptor sites or two or more discrete channels.